A radiotherapy apparatus for treating a cancer and a tumor by using radiation has been well known. As a three-dimensional irradiation radiotherapy apparatus for carrying out an irradiation at a stereotactic multiple arc, there are a radiosurgery treating apparatus, a linac (medical linear accelerator) treating apparatus and the like.
Here, the stereotactic multiple arc irradiation designates the radiotherapy method that intensively irradiates the radiation to a small focus from many directions and thereby improves the treatment effect, and further minimizes the exposure amount of ambient tissues. Its power is exerted on the treatment for a primary benign brain tumor, a single metastatic brain tumor whose size is 3 cm or less, a small lesion inside a brain such as a cranial base metastasis whose operation is difficult, an artery malformation, a vein malformation or the like.
The radiosurgery treating apparatus intensively irradiates a thin radioaction beam to a particular small region at a very high accuracy, from one or more radiation irradiating units fixed to the treating apparatus. As the radiation irradiating unit, a gamma-ray source or a linac are used.
In the radiosurgery treating apparatus, by using a precisely positioning/affected part immobilization device serving as an immobilization device for the stereotactic radiation irradiation, the affected part of a cranial bone of a patient and a part around the affected part are mechanically fixed. Then, by using this frame as a coordinate standard tool for the positioning, taking images for diagnosing such as X-ray CT (Computed Tomography), MRI, DAS (Digital Subtraction Angiography) and the like, is carried out to thereby deduce the accurate position and shape of the affected part. Then, the patient is mechanically fixed in an irradiating apparatus composed of: one or more radiation irradiating units; and a collimating mechanism for collimating them and concentrating the treating radiation on the small region in space, while this frame is kept. Consequently, the irradiation field is matched with the small region mechanically and precisely so that the stereotactic irradiation is precisely carried out. If a treatment field is spherical, a necessary treatment dosage can be irradiated at one time. If the treatment field is indeterminate, correspondingly to the shape of the treatment field, the positioning operation is repeated several times. At the same time, an aperture of a collimator is newly selected each time, and the irradiating treatment is carried out.
In the radiosurgery treating apparatus, the apparatus and the procedure are very simple, and the high reliability can be obtained. Together with them, if an irradiation target is not moved against the cranial bones such as a head portion, the positioning and irradiating operations can be extremely precisely performed. However, the irradiation field of the radiation irradiating unit is fixed, thus, the stereotactic irradiating treatment is not performed on the body part, in which the irradiation field at the tumor, the malformation and the like, is moved by the influence of the motion and the condition of organs such as a breath and a cardiac beat, a peristalsis, a urine amount within a urinary bladder and the like below a chin. Strictly, the radiation is not irradiated while the affected part is observed at real time.
In the linac treating apparatus, a large gantry rotates around one axis parallel to its installation surface by 360 degrees to thereby carry out an isocentric irradiating treatment. In addition, various irradiation can be carried out by adding the two-dimensional movement within vertical and horizontal planes of a treatment bed and the rotation within the horizontal plane. Also, by MLC (Multi Leaf Collimator), the irradiation field having a complex shape can be handled, and the precisely irradiating treatment (IMRT: Intensity Modulated Radio Therapy) can be carried out by controlling an irradiation dosage distribution.
The linac treating apparatus can not carry out a high speed position control. For this reason, a follow-up irradiation at real time can not be performed on the treatment field moving at a high speed, such as the movement caused by the cardiac beat. Also, a linac graphics through a transmission radiation of treatment X-rays is used as a monitor for the treatment field during the irradiation. Since the treatment X-ray has a property of a strong transmission and generates much scattered radiations, the image quality for the real time monitor in the irradiation field is not high.
A synchronous irradiation is performed by using a breath synchronizing apparatus in case of only a breathing motion. This can not image the image of the affected part at real time, thus, the position of the affected part is estimated by using a preset method. When the affected part is estimated to arrive at a preset irradiation position, the irradiating unit is triggered so as to carry out the treatment irradiation. As the estimating method, a marker put on the affected part is optically pursued. Or, the flow amount of exhalations is directly measured to grasp the breathing state of the patient to thereby estimate the movement of the affected part.
However, in the synchronous irradiation, the position of the affected part is estimated and the radiation is irradiated toward the estimated position. Thus, the radiation are not irradiated while the affected part is pursued at real time.
An apparatus for isocentrically driving an electron linac and an apparatus for driving an electron linac along a gantry having a preset shape are known as other three-dimensional irradiating radiotherapy apparatuses.
As the apparatus for isocentrically driving the electron linac, there is the apparatus including a small electron linac at a tip of an industrial general robot arm. The accurate shape and position of the affected part are deduced by correlating to a marker such as a small gold plate which is embedded as a sign near the affected part, and a landmark of the body organization such as a cranial bone and a breast, through an X-ray CT and MRI. Then, at the time of the treatment irradiation, the apparatus, while using two X-ray cameras with different visual lines and monitoring the motion of the landmark and then correcting a collimation, carries out the precise irradiation. This apparatus can essentially carry out the non-isocentric irradiating treatment through a freely moving performance of a six-degree-of-freedom robot arm.
Even though this apparatus uses a immobilization device for fixing the head part in a case of a treatment of the head part, it does not irradiate the radiation while directly observing the image of the affected part. That is, it does not photograph by using the X-ray camera during the irradiation of the treatment beam. For this reason, it employs the method of completing the photographing prior to the start of the irradiation, and confirming the irradiation position, and then starting the irradiation. Thus, also in this case, the irradiation field is not monitored at the real time. Also, since the electron linac is heavy in weight, the problems regarding the inertia and the like need to be solved, in order to perform the precise follow-up irradiation at the real time on the quick motion such as the cardiac beat while keeping the electron linac at the tip of the robot arm having cantilever structure.
Also, the industrial robot arm does not insure the absolute precision on a specified space coordinate, but it only insures a repetitive precision through teaching. Thus, the teaching and the work related thereto are required prior to the actual treatment.
The apparatus for driving the electron linac along the gantry having the preset shape is disclosed in, for example, Japanese Laid Open Patent Application (JP-A-Heisei 8-504347 (International Application Number: PCT/US93/11872)) and Japanese Laid Open Patent Application (JP-A-Heisei 6-502330) International Application Number: PCT/US91/07696)). This includes a C-arm type X-ray camera having two rotational axes and a medical electron linac similarly having two rotational axes. A three-dimensional irradiation can be carried out by further adding a different rotational axis to a conventional electron linac that can carry out only a rotation in one axis direction. The irradiating method is similar to the case of the radiosurgery treating apparatus in that it is isocentric and the head portion needs to be fixed by the frame. However, it is different from the case of the radiosurgery treating apparatus in that the large gantry is driven by the two axes.
The affected part of the patient is being moved even during the treatment. In particular, below the chin, the irradiation target such as the tumor or the like is always moved by the influence of the motion and the condition of the organs, such as the breath, the cardiac beat, the peristalsis and the urine amount within the urinary bladder. For example, only when the patient lies, the body becomes gradually flat. Moreover, although the breath and the cardiac beat that are cyclic motions are cyclic, the motions of the respective organs associated with the cyclic motions do not always pass through the same routes every time.
On the other hand, in order to accurately capture the motion of the irradiation target at the real time, it is said that a technique for photographing images at a rate of about 30 images per second is required since the cardiac beat that is one of the fastest motions is one to two times per second. Then, if accurately pursuing the irradiation target at the real time and irradiating the radiation, it is necessary to accurately train a radiation irradiating head on the irradiation target for each 1/30 second.
Even if the treatment field of the radiation is being moved, the technique is required which can irradiate the radiation while pursuing the treatment field. The technique is desired which can monitor the state of the treatment field at the real time. The technique is desired which can carry out the quick collimation adjustment from a region of a wide region and execute the radiation irradiation. And, the technique is desired which can reduce the burden of the radiation irradiation on the patient while improving the treatment effect.
Therefore, an object of the present invention is to provide a radiotherapy apparatus which can irradiate the radiation while pursuing the treatment field, even if the treatment field of the radiation is being moved.
Another object of the present invention is to provide a radiotherapy apparatus that can monitor the state of the treatment field at the real time even during the irradiation treatment of the radiation.
Still another object of the present invention is to provide a radiotherapy apparatus that can carry out the quick collimation adjustment from the region of the wide region and execute the radiation irradiation, as well as the irradiation around the single rotational axis and the isocentric irradiation.
Yet still another object of the present invention is to provide a radiotherapy apparatus that can accurately irradiate the radiation and meanwhile improve the treatment effect and reduce the burden on the patient.